1. Field of the Invention
This invention relates to a patch antenna for receiving high frequency wireless signal and a rectenna using the same, more particularly, to an impedance-matched patch antenna adopting a slot capacitive coupling structure and a rectenna capable of generating electrical energy from the wireless signals having different frequency band.
2. Description of the Related Art
A patch antenna according to the first example of prior art is illustrated in FIG. 1. A patch antenna 10 illustrated in FIG. 1 adopts an in-set structure, wherein impedance matching is achieved by adjusting design parameters (a, b) of the gap 122 formed at each side of the feeder line 121 that is a partial extension from the bottom side of the patch 12 which is formed on a surface of the dielectric substrate 11.
According to the first example of prior art, forming the minute gaps at both sides of the feeder line 121 is a very difficult process; furthermore, the impedance matching condition gets easily out of control due to a small variation in process parameters during actual fabrication of a patch antenna.
In addition, since the gaps 122, located at the both sides of the feeder line 121 which is an impedance matching means, are formed inside the patch 12 as an integrated part thereof, the expensive patch 12 has to be newly fabricated in case when a problem occurs during the gap forming process.
A patch antenna according to the second example of prior art is illustrated in FIG. 2. The patch antenna 20, having a dual frequency band characteristics, of the second example of prior art is comprised of an dielectric substrate 21, an external patch 22, and an internal patch 23 as illustrated in FIG. 2.
The patch antenna 20 of the second example of prior art is capable of transmitting and receiving both signals having two different frequency bands by adopting an external patch 22 and an internal patch 23 having different frequency characteristics.
But, since this type of patch antenna utilizes two patches in transmitting and receiving signals having two different frequency bands, it requires high production cost and large antenna size to integrate two types of patch into a stacked form.
A rectenna according to an example of the prior art is illustrated in FIG. 3. The rectenna 30, shown in FIG. 3, relates to a rectenna that utilizes a loop antenna; it is largely comprised of a loop antenna 31 and a rectifying circuit 32; it converts an A.C. wireless signal received via the loop antenna 31 into a D.C. electrical energy by rectifying the A.C. wireless signal in the rectifying circuit 32, and supplies this electrical energy to the load 33.
Since such rectenna 30 of the prior art has only one frequency characteristics depending on the characteristics of the loop antenna 31, the electrical energy cannot be supplied to the load 33 if a wireless signal having the frequency band matched in frequency characteristics of the rectenna 30 is not received.
Furthermore, the rectenna 30 of the prior art simply rectifies the received wireless signal, so the wireless signal must be amplified before transmitting the wireless signal to the rectenna 30 when the load 33 needs a high voltage.